It is known in the state of the art to use a circuit apparatus comprising at least two oscillators coupled by means of a proper network. The main applications of such an apparatus are the implementation of both quadrature signals and voltage-controlled oscillators with low phase-noise. For this approach, the design of the coupling network is the main issue. The coupling network may be of the active type, as disclosed in Jeong Ki Kim et al., “A current-reuse quadrature VCO for wireless body area networks,” IEEE/NIH LiSSA, pp. 55-58, 2011 (the disclosure of which is incorporated by reference), or capacitive type as disclosed in Oliveira, L. B. et al., “Synchronization of two LC-oscillators using capacitive coupling,” IEEE ISCAS, pp. 2322-2325, 2008 (the disclosure of which is incorporated by reference), or inductive type as disclosed in Tzuen-Hsi Huang et al., “A 1 V 2.2 mW 7 GHz CMOS quadrature VCO using current-reuse and cross-coupled transformer-feedback technology,” IEEE MWCL, vol. 18, pp. 698-700, October 2008 (the disclosure of which is incorporated by reference).
Also it is known in the state of the art to use a power combining techniques to increase the overall output power in several applications. Due to technology limits, (e.g., breakdown, electro-migration constraints, thermal issues, etc.) the power level delivered by a single power stage is often below the application requirements, thus a multistage solution is required. When it comes to dc/ac conversion, transformer-based power-combining is the straight-forward solution. An example of power-combining system is disclosed in Tomita et al., “1-W 3.3-16.3-V boosting wireless power oscillator circuits with vector summing power controller,” IEEE JSSC, vol. 47, pp. 2576-2585, November 2012 (the disclosure of which is incorporated by reference), where two power stages separately drive two series resonant circuits and both drivers are magnetically coupled with the secondary inductance. By controlling the phase relation between the driver's signals, the output power can effectively reach two times the power delivered by a single stage.
The use of transformer-based systems to perform data communication and/or power transfer through a galvanic barrier is known in the art. Some fields of application for such systems include industrial applications, medical devices, sensors, lighting, or any application involving galvanic isolation.
For example, systems that employ multiple transformers to create multiple isolated channels for bidirectional communication are known. While these systems are useful, they employ multiple transformers, and separate power transfer and data transfer into separate transformer links. This may increase the cost of these systems as well as the space occupied by these systems. Accordingly, further advances in transformer-based systems that perform data and power transfer through galvanic barriers are desired.